Lo Chun-Min, Buxton Denis B, Chua Gregory C H, Dembo Micah, Adelstein Robert S, Wang Yu-Li
Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
Mol Biol Cell. 2004 Mar;15(3):982-9. doi: 10.1091/mbc.e03-06-0359. Epub 2003 Dec 29.
Although myosin II is known to play an important role in cell migration, little is known about its specific functions. We have addressed the function of one of the isoforms of myosin II, myosin IIB, by analyzing the movement and mechanical characteristics of fibroblasts where this protein has been ablated by gene disruption. Myosin IIB null cells displayed multiple unstable and disorganized protrusions, although they were still able to generate a large fraction of traction forces when cultured on flexible polyacrylamide substrates. However, the traction forces were highly disorganized relative to the direction of cell migration. Analysis of cell migration patterns indicated an increase in speed and decrease in persistence, which were likely responsible for the defects in directional movements as demonstrated with Boyden chambers. In addition, unlike control cells, mutant cells failed to respond to mechanical signals such as compressing forces and changes in substrate rigidity. Immunofluorescence staining indicated that myosin IIB was localized preferentially along stress fibers in the interior region of the cell. Our results suggest that myosin IIB is involved not in propelling but in directing the cell movement, by coordinating protrusive activities and stabilizing the cell polarity.
尽管已知肌球蛋白II在细胞迁移中起重要作用，但其具体功能却鲜为人知。我们通过分析基因敲除该蛋白的成纤维细胞的运动和力学特性，探讨了肌球蛋白II的一种同工型——肌球蛋白IIB的功能。肌球蛋白IIB基因敲除的细胞表现出多个不稳定且无序的突起，尽管当它们在柔性聚丙烯酰胺底物上培养时仍能产生大部分牵引力。然而，相对于细胞迁移方向，牵引力高度无序。细胞迁移模式分析表明速度增加而持续性降低，这可能是导致如博伊登小室实验所证明的定向运动缺陷的原因。此外，与对照细胞不同，突变细胞对诸如压缩力和底物硬度变化等机械信号无反应。免疫荧光染色表明肌球蛋白IIB优先定位于细胞内部区域的应力纤维上。我们的结果表明，肌球蛋白IIB不是参与推动细胞运动，而是通过协调突出活动和稳定细胞极性来指导细胞运动。
